The present invention relates to improvements in acoustic transducers of the electromagnetic type including plane-driving type diaphragms, which are intended for use in loudspeakers, earphones, head phones or mocrophones.
For example, an acoustic transducer of the electromagnetic type that includes a vibratable diaphragm having a conductor and disposed within a magnetic field defined by a permanent magnet is described in U.S. Pat. No. 3,919,498 specification. In the transducer of this type, since the diaphragm is secured through a suitable fixing member to the magnet which faces it at its entire peripheral edge and its center, the entire peripheral edge and the center undergo no vibration so that the diaphragm is not plane-driven. Consequently, the transducer of this type is disadvantageous in that the amplitude of the diaphragm is small, resulting in unfaithful reproduction of a low sound range and that the allowable input cannot be raised. The present invention provides an electromagnetic type acoustic transducer which avoids these and other drawbacks.